1. Field of the Invention
The present invention relates to communication systems, and more specifically to a method and apparatus to reduce noise and distortion in a receiver system.
2. Related Art
Receiver systems (e.g., wireless or wired systems) receive signals from various sources, and process the received signal to recover the information encoded in the received signals. In general, a signal of interest (e.g., encoding the information) is present in a frequency band of interest of the received signals. The received signals typically also contain unwanted signals outside of the frequency band of interest.
The signals of interest (when received at receiver systems) are often weak due to factors such as distance between a transmitter (sending the signals) and the receiver, the strength with which the transmitter generates the signals, etc. Such a weak signal needs to be amplified with filtering before processing, at least to avoid the effect of strong interference signals, which have frequencies adjacent (close) to the frequency band of interest.
In general, receiver systems perform various operations such as amplification and filtering to amplify the weak signals of interest and to remove the remaining unwanted signal components. The generated amplified signal of interest is provided for further processing. Due to the operations (amplification and filtering), the effect of interference signal may be avoided.
Such operations generally need to be implemented while meeting various objectives. One such objective is to minimize/avoid introduction of additional noise (into the signal of interest). Noise refers to an undesirable signal component introduced along with (or into) the signal of interest, and is often formed/introduced by components which perform the operations.
Another objective while performing such operations is minimize/avoid introduction of additional distortion. In general, when the input signal is subject to operations such as amplification, there needs to be a linear response (e.g., same amplification factor during amplification operation). Deviations from the linear response (or any desired response, in general), is referred to as distortion. By minimizing the distortion, the resulting (amplified) signal would accurately represent the information in the signal of interest.
One source of such distortion (non-linearity) is the non-linear characteristics of components such as transistors. For example, transistor clips the peak voltage of the received (or amplified) signals if the voltage swing is large. However, a large voltage swing is desirable to reduce the effect of noise, and a low voltage swing is desirable to reduce distortion.
What is therefore required is a method and apparatus to reduce both noise and distortion in receiver systems.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.